1. Field of the Invention
The present invention relates to inorganic minerals useful for animal nutrition. More particularly, it relates to a new water soluble bioavailable feed mineral composition of alkali metal magnesium phosphate hydrate which provides effective buffering in the digestive fluids of animals. The new composition may be represented by the empirical formula LxMgyHz (PO4)xc2x7W H2O wherein L represents an alkali metal, X represents numbers between 0.50 and 3.7, Y is between 0.50 and 1.50, Z is between 0.00 and 1.50, and W represents numbers between 0.60 and 1.50. An effective method for preparing the new composition is provided.
2. Description of Related Art
The elements phosphorus, magnesium, and alkali metals are all essential parts of the mineral requirements of animals. These elements are frequently supplied in feed rations in the form of a mineral mixture containing dicalcium phosphate and sodium chloride. The dicalcium phosphate sometimes provides more calcium than is desirable in some feed rations and a non-calcium phosphorus source is needed. Monosodium phosphate is used in some rations to supply phosphorus without calcium, but undesirably exhibits an acid pH.
Animals feeding on high energy rations need buffering to maintain pH in their digestive fluids in an optimum range between 6 and 7. A common buffering practice is to add sodium bicarbonate exhibiting a pH of between 8.5 to 9.5 to buffer the pH of these fluids to the desired area. Sodium bicarbonate contributes only sodium as a nutrient and becomes spent if applied to damp rations such as silage.
Phosphorous, magnesium, and alkali metal ions are supplied as feed mineral concentrates for animals in several different ways. For example, in U.S. Pat. No. 4,027,043 and 4,431,675 J. J. Schroeder et al disclose a solid animal feed supplement comprising a small amount of soluble phosphate, an oxide of a metal consisting of aluminum, magnesium, or calcium with molasses and fat to form a solid block in which a substantial amount of protein equivalent, such as urea, is combined. The mineral blocks thus formed exhibit acid pH""s which provide little or no buffering in the desired fluid pH range for animals. The blocks also contain little or no soluble magnesium.
In my U.S. Pat. No. 5,613,465 and 5,374,294 the preparation of controlled release fertilizers with very low water solubilities by combining alkali metal ions, phosphoric acid and divalent metal oxides, particularly magnesium oxide, is disclosed.
Soluble phosphates provided as monosodium phosphate usually contain 20 to 30 percent pyrophosphate, which must be slowly dissolved and hydrolyzed to allow assimilation as orthophosphate. The acidity of the monosodium phosphate provides no buffering of rumen fluids in the desired pH range.
Heretofore, workers in the art have not been able to combine alkali metals such as sodium with magnesium and phosphorus to form a bioavailable water soluble composition which functions as an effective buffer for digestive fluids of animals in the optimum pH range. Such a composition is to be highly desired, because it would allow an economically small amount of mineral to be admixed in the feed ration to safely buffer digestive fluids in the optimum pH range while effectively providing the required magnesium and phosphorus moieties of the feed rations in highly available form.
It is a primary object of this invention to provide a feed mineral composition to provide magnesium, phosphorus, and alkali metal elements for animals in bioavailable form.
It is another primary object of this invention to provide a feed mineral composition which will provide buffering of digestive fluids of animals to about an optimum pH for feed utilization.
It is another object of this invention to provide a bioavailable buffering feed mineral composition prepared in a simple method from commodity chemicals.
I have discovered a new water soluble animal feed mineral composition which provides highly bioavailable phosphorus, magnesium, and alkali metals, such as sodium and potassium, while buffering the digestive fluids of animals to near neutral pH with a wide margin of safety. The new composition is an alkali metal magnesium phosphate hydrate which provides a total of between 1.50 and 4.70 equivalent weights of alkali metal and magnesium per molecule of phosphorus and may be represented by the empirical formula LxMgyHz (PO4)xc2x7W H2O wherein L represents an alkali metal, X represents numbers between 0.50 and 3.7, Y represents numbers between 0.50 and 1.50, Z represents numbers between 0.00 and 1.50, and W represents numbers between 0.60 and 1.50.
The new composition, providing safe buffering of digestive fluids and high bioavailability of phosphorus, magnesium, and alkali metal, may be effectively prepared from commodity chemicals. The preparation comprises reacting alkali metal bases and strong aqueous phosphoric acid, and then reacting the alkali metal phosphate formed with magnesium oxide powder to produce alkali metal magnesium phosphate hydrate. To preserve the composition""s water solubility, the hydrate product is dried only until the water amounts to between 0.6 and 1.50 mols in the alkali metal magnesium phosphate hydrate empirical formula.
The instant invention is a bioavailable water soluble animal feed mineral composition which comprises an alkali metal magnesium phosphate hydrate providing a total of between 1.50 and 4.70 equivalent weights of alkali metal and magnesium per molecule of phosphorus which may be represented by the empirical formula LxMgyHz (PO4)xc2x7W H2O wherein L represents an alkali metal moiety, X represents numbers between 0.50 and 3.7, Y represents numbers between 0.50 and 1.50, Z represents numbers between 0.00 and 1.50, and W represents numbers between 0.60 and 1.50, the composition providing buffering of digestive fluids of ruminant and monogastric animals to near neutral pH""s.
The presence of an alkali metal, usually sodium or potassium, in amounts between 0.50 and 3.70 molecules per empirical formula provides high bioavailability for the composition. Smaller amounts drastically reduce the water solubility and the magnesium and phosphorous bioavailability, and larger amounts increase hygroscopicity of the composition causing poor storage stability.
The retention of hydrogen in the composition is usually not desirable for maximum buffer capacity but up to 1.50 molecules may be retained to buffer at low pH""s and still retain high bioavailability. More than 1.50 molecules of hydrogen provides unsatisfactory buffering in the digestive fluids.
A key to water solubility and bioavailability is the water of hydration in the instant composition. Water solubility and bioavailability of magnesium and phosphorus decrease sharply as the water of hydration is decreased to less than 0.60 molecule per empirical formula and the storage stability decreases sharply as water of hydration is increased to more than 1.50 molecules per empirical formula.
The molecular weight of the alkali metal, sodium or potassium for example, included in the animal feed mineral formula has an effect on its weight percent content, but the composition is effective with the alkali metal amounting to between 8 and 39 percent, the magnesium amounting to between 7 and 19 percent, the phosphorous amounting to between 13 and 20 and the water amounting to between 6 and 12 percent of the composition.
The composition is effective where the phosphorus is derived from economical wet process orthophosphoric acid. For safe effective use as an animal feed mineral, it is necessary that the orthophosphoric acid contain less than 1 part of fluoride per 100 parts of phosphorus. Furnace grade orthophosphoric acid may also be effectively used but it is economically less desirable. The use of pyrophosphoric acid is not effective because the compositions formed are very difficult to recover in dry granular form and must be hydrolyzed back to orthophosphates before they may be utilized.
The instant feed mineral compositions are effective when the alkali metal is derived from alkali metal bases such as sodium carbonate or potassium hydroxide and when the magnesium is derived from magnesium bases such as magnesium oxide or magnesium hydroxide.
The composition is particularly effective and economical where the alkali metal is sodium. The efficacy is especially high where the alkali metal is derived from sodium carbonate and the magnesium is derived from magnesium oxide.
Materials frequently used in the art to buffer digestive fluids are sodium bicarbonate and magnesium oxide. These commercial compounds exhibit high pH""s in water, and if ingested in excess can quickly cause undesirable alkaline conditions in the digestive fluids. Over-treatment with buffer may be caused by errors in estimates of animal size, and the composition of the digestive fluid and by errors in measuring the amounts of the buffering material. The instant composition exhibits a pH of between 6.6 and 10.0 when diluted to a 5 percent distilled water solution; however, it slowly buffers acid pH in digestive fluids without the quick high pH reaction possible with buffers such as sodium carbonate, magnesium oxide and sodium bicarbonate.
Best properties of bioavailability, buffering of digestive fluids, and storage stability are obtained with the preferred composition which is represented by the empirical formula LxMgyHz (PO4)xc2x7W H2O wherein L represents an alkali metal, X represents numbers between 0.90 and 3.07, Y represents numbers between 0.50 and 1.50, Z represents numbers between 0.00 and 0.30, and W represents numbers between 0.60 and 0.80.
The alkali metal magnesium phosphate hydrate preferably provides a total of between 2.7 and 4.7 equivalent weights of alkali metal and magnesium per molecule of phosphorus in the instant composition to obtain excellent buffering of animal digestive fluids.
The effective instant composition may be prepared by a method comprising admixing particulate alkali metal base with aqueous wet process orthophosphoric acid containing between 50 and 60 percent phosphorus, expressed as P2O5. The admixing is continued until the alkali metal base and the orthophosphoric acid react to form aqueous alkali metal orthophosphate. An amount of magnesium oxide powder containing between 54 and 60 percent magnesium is admixed and reacted with the aqueous alkali metal orthophosphate so that a total of between 3.0 and 4.0 equivalent weights of alkali metal and magnesium are combined with each molecule of phosphorus.
The mixing is continued until homogeneous particles of alkali metal magnesium orthophosphate hydrate are formed. Then, the particles are dried by ordinary means until animal mineral particles are formed which exhibit an empirical formula of LxMgyHz (PO4)xc2x7W H2O wherein L represents an alkali metal, X represents numbers between 0.90 and 3.0, Y represents numbers between 0.50 and 1.50, Z represents numbers between 0.00 and 0.30, and W represents numbers between 0.6 and 0.8.
A particularly economical storage stable bioavailable and water soluble sodium magnesium orthophosphate hydrate animal feed mineral buffering composition exhibiting an empirical formula of about Na2 Mg H (PO4)xc2x70.8 H2O is prepared by the following stepwise method. First, sodium carbonate containing between 40 and 47 percent sodium is admixed with aqueous wet process orthophosphoric acid containing between 50 and 60 percent P2O5 at a molecular ratio of about 2.0 sodium to 1.0 phosphorus.
Admixing is continued until reaction between sodium carbonate and orthophosphoric acid is complete as indicated by termination of carbon dioxide generation, to form aqueous sodium orthophosphate. Then, admixing and reacting an amount of magnesium oxide containing between 54 and 60 percent magnesium, with the aqueous sodium orthophosphate so that the molecular ratio of sodium to phosphorus to magnesium amounts to about 2 to 1 to 1. Continuing to admix until homogeneous particles of sodium magnesium phosphate hydrate are formed, and then drying by conventional means until a particulate animal feed mineral buffering composition is formed containing about 0.8 molecule of water per empirical formula.
The utility of the animal feed mineral composition may be optimized for particular animals and for particular feeding situations by partitioning the mineral composition solids into a plurality of particle size ranges by means of a screener.
The size of the animal mineral particles may be controlled where the fine dry animal mineral particles partitioned by means of a screener and passing through a 20 Mesh U.S. Standard Screen, amounting to between 10 and 50 percent of the animal mineral particles are recycled and admixed with the sodium magnesium orthophosphate hydrate before drying to control the size of the animal mineral particles.
The instant composition may be prepared in a particularly effective manner by a method wherein the admixing and reacting to form homogeneous particles is performed in a pan rotating clockwise at a tip speed between 0.5 and 10.0 meters per second at an angle between 10 and 30 degrees from horizontal, with the pan equipped with an agitator exhibiting a diameter between 20 and 33 percent of that of the pan and operating near the wall of the pan in a counterclockwise direction at a tip speed between 2 and 5 times that of the pan.